1. Field of the Invention
The present invention relates to a pouring tube for feeding molten steel into the pouring zone of a mold consisting of broad side walls and narrow side walls, particularly for casting thin steel slabs. The pouring tube includes a tube portion connected to a pouring container and an end portion which is provided with outlet openings directed toward the narrow side walls and a bottom piece at the end face of the pouring tube.
2. Description of the Related Art
In a pouring tube known from DE-A 37 09 188, to the cylindrical tube portion is connected a flattened end portion having slot-like outlet openings and a bottom piece with a raised inner contour. The extension of the bottom piece in the direction of the outlet openings is greater than the distance between the walls which form the upper limit of the outlet openings.
Although the known pouring tube is of complicated and expensive construction, it is not capable of providing the necessary operating safety and service life because of the high demands made during continuous steel casting. The molten steel emerges from the narrow outlet openings in concentrated form with a kinetic energy which is too high. As a result, particularly in a thin steel slab casting mold, washings may occur at the strand shell which is still thin and a surge wave may occur in front of the narrow side walls. Moreover, the uneven flow distribution within the mold occurring when pouring with the known pouring tube results in the formation of an irregular surface structure.
The present invention starts from the finding that the reason for the non-uniform, unstable molten steel distribution within the mold is the uneven speed with which the molten steel is discharged over the cross-sectional areas of the outlet openings.
Since the discharge speed is the greatest at the lower portion of the outlet slot, a strong vortex each is formed underneath the outlet openings and corresponding upwardly directed compensating flows occur in front of the short side walls which lead to a surge wave on the bath surface.